The general health benefits of eating fruit and vegetables are well known, but researchers have provided young women with yet another reason to eat their greens. A large-scale study carried out by the Harvard T.H. Chan School of Public Health, which followed thousands of women for several years, has found a strong correlation between a high-fiber diet during adolescence and young adulthood and a reduced risk of developing breast cancer later in life.

The findings were based on data from 90,534 women who participated in the Nurses' Health Study II, a long-running study of the factors that have an impact on women's health. The study goes back to 1991, when women aged 27-44 were recruited to answer four-yearly questionnaires about their food intake. In 1998 they also completed a questionnaire about their diet during high school.

The researchers also factored in other variables such as race, history of breast cancer in the family, body mass index, weight fluctuation and several other bits of information. When they analyzed the data, the researchers found compelling evidence of the benefits of a diet high in fiber in helping prevent the disease.

For instance, when women ate more fiber-rich food types in early adulthood, their risk of breast cancer lowered by between 12 and 19 percent. If their fiber intake was high during adolescence, the overall risk of developing the cancer at any point in their lives was reduced by 16 percent, with a 24 percent lower risk of developing it before menopause.

Quantity also matters, the study revealed. The higher the quantity of fiber a woman consumed in early adulthood, the less likely they were to develop the disease. In statistical terms, the researchers said that for each additional 10 grams of fiber intake daily during that time in their lives, risk of breast cancer dropped by 13 percent.

Fiber from fruit and vegetables was found to produce the greatest benefits. The study authors believe this is because they help reduce high estrogen levels in the blood, which has been linked with breast cancer development.

"From many other studies we know that breast tissue is particularly influenced by carcinogens and anticarcinogens during childhood and adolescence," says Walter Willett, the study's senior author. "We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk."

The study was published in the March issue of the journal Pediatrics.